My immediate goal is to acquire the necessary skills and expertise in molecular and translational research during the mentor phase to develop a career transition to independence in the area of antibiotic resistance and molecular pathogenesis of bacteria. The long term goals of this work are to translate in vitro and in vivo observations relating to virulence and pathogenesis into new and useful strategies to combat severe enterococcal infections in humans in the era of antibiotic resistance. Enterococcus faecium (Efm) have emerged as one of most difficult organisms to treat in US hospitals due to resistance to multiple antibiotics. Previous research has identified a plasmid-encoded putative hyaluronidase gene which is exclusively found in hospital isolates of Efm and is also more frequently present in isolates from the USA (as opposed to European ones). The hyalurodinase group of enzymes are well known pathogenic determinants in Gram-positive bacteria. Experiments in a mouse peritonitis model confirmed that an Efm containing the hyl-like plasmid was significantly more lethal than isogenic isolates lacking this plasmid. An Efm hyl-deletion mutant was attenuated in the same animal model. Anti-"Hyl" antibodies have been shown to be protective against challenge of Efm in animal models. The hypotheses for this proposal are: i) the hyl-like gene (or some other component of the plasmid) contributes to the recently observed success of Efm in hospital acquired infections and ii) virulence determinants (like "Hyl", if its role in virulence is confirmed) could be used as targets to develop novel therapeutic approaches. The specifc aim for the mentored part of this project is to define the role and contribution of the hyl-like gene to virulence in Efm. The aims for the independent part of this proposal include to: i) evaluate an antibody-antibiotic approach to treat Efm infections using translational tools in animal models and also, ii) explore the possible role in virulence of genes other than hyl in the hyl-containing plasmid (if hyl turns out not to explain all the virulence properties of the plasmid). These aims will be addressed by means of developing tools for genetic manipulation of Efm isolates and testing the mutants in animal models to characterize the role of hyl-knockouts (or other genes as appropriate) in virulence. A translational approach using the mentor's laboratory established animal models (mouse peritonitis and rat infective endocarditis) will be utilized to explore therapeutic approaches. [unreadable] [unreadable] [unreadable]